Jun 2014, Volume 8 Issue 2
    

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  • RESEARCH ARTICLE
    Maotian LI, Jianzhong GE, Jens KAPPENBERG, Dagmar MUCH, Ohle NINO, Zhongyuan CHEN

    The Digital Elevation Model (DEM) based on the historical sea-charts and on-site hydrological records were used to examine the morphological change of the Elbe River estuary. The results show that siltation predominated in the tidal flat in the northern estuary, with a net siltation rate of 1.8 cm·a−1 during 1927–2006. In contrast, a continuous erosion prevailed in the main river channel, south of the estuary, with a net erosion rate of 2.5 cm·a−1 in the same time. In addition, a seaward shift of the estuarine island has happened with the old island coalescing to the northern tidal flat and new one emerging through siltation process. The tidal asymmetry via ebbing flow (maximum at 140 cm·s−1, and average at 76 cm·s−1) prevailed in the tidal flat, meaning continuous aggradation northwestward, while flooding flow (maximum at 100 cm·s−1, and average at 67 cm·s−1) dominated in the main river channel with deepening thaweg at south, showing a landward sedimentation via the tidal pumping processes. This dextral extension of the estuarine morphology is due to the Coriolis force, leading to the inconsistent directions of in-out flows, which enables to facilitate the estuarine siltation. Human dredging prevailing in the estuary has dramatically altered the nature of the silted river channel to erosional since the last century. This is characterized by a net erosion rate of 3.2 cm·a−1 derived from the DEMs mapping, but only partially accounting for the dredging amount of 1994–2006, when the total dredging volume was 67 × 106 m3, equal to 5.9 cm·a−1.

  • RESEARCH ARTICLE
    Yan ZHANG,Hong LIU,Bin CHEN,Hongmei ZHENG,Yating LI

    Discovering ways in which to increase the sustainability of the metabolic processes involved in urbanization has become an urgent task for urban design and management in China. As cities are analogous to living organisms, the disorders of their metabolic processes can be regarded as the cause of “urban disease”. Therefore, identification of these causes through metabolic process analysis and ecological element distribution through the urban ecosystem’s compartments will be helpful. By using Beijing as an example, we have compiled monetary input–output tables from 1997, 2000, 2002, 2005, and 2007 and calculated the intensities of the embodied ecological elements to compile the corresponding implied physical input–output tables. We then divided Beijing’s economy into 32 compartments and analyzed the direct and indirect ecological intensities embodied in the flows of ecological elements through urban metabolic processes. Based on the combination of input–output tables and ecological network analysis, the description of multiple ecological elements transferred among Beijing’s industrial compartments and their distribution has been refined. This hybrid approach can provide a more scientific basis for management of urban resource flows. In addition, the data obtained from distribution characteristics of ecological elements may provide a basic data platform for exploring the metabolic mechanism of Beijing.

  • RESEARCH ARTICLE
    Guiting HOU, K. R. HARI

    The Bohai Sea is a Late Mesozoic-Cenozoic feature of the basin-mountain system located in eastern North China Craton (NCC). The Late Mesozoic thinning of the lithosphere signals the early destruction of the NCC. The onset of the destruction was due to the delamination of thick lithosphere of the craton, represented by the NW-trending grabens in an en-echelon arrangement west to Tanlu Fault, and by the NNE-trending grabens within the Tanlu Fault Zone. The Late Mesozoic NW-trending grabens are overprinted by structures related to the Cenozoic NE-trending pull-apart basin with very thick Mesozoic-Cenozoic sediments in the eastern NCC. C-frequency diagrams of growth faults and the extension factor (β) of four sections across the basin suggest that the extension migrated from the margin to the center of Bohai Sea, and that the Mesozoic and Cenozoic extension factors for Bohai Sea are higher than that of the margin. These evidences suggest that the greatest extension occurred in the center of Bohai Sea, which is consistent with the thinnest crust being found in the center of the sea. The extension ratios and tectonic evolution of the Bohai Sea suggest that it is the key region for the destruction of the NCC, as evidenced by the topography. However, the NCC experienced two stages of destruction with the late stage related to the tectonic regime of Northeast Asia.

  • REVIEW ARTICLE
    Chunqing SUN, Haitao YOU, Jiaqi LIU, Xin LI, Jinliang GAO, Shuangshuang CHEN

    Large explosive volcanic eruptions generate extensive regional tephra deposits that provide favorable conditions for identifying the source of volcanoes, comparing the sedimentary strata of a region and determining their ages. The tephra layer, referred to as B-Tm, generated by the Millennium eruption of Changbaishan volcano, is widely distributed in Northeast China, Japan, D.P.R. Korea, and the nearby coastal area of Russia. It forms part of the widespread northeast Asian strata and is significant for establishing an isochronal stratigraphic framework. However, research on the temporal characterization and stratigraphic correlation of associated strata using this tephra layer is mainly concentrated in and near Japan. In northeastern China, this tephra layer is seldom seen and its application in stratigraphic correlations is even rarer. More importantly, the determination of accurate ages for both distal and proximal tephras has been debated, leading to controversy in discussions of its environmental impacts. Stratigraphic records from both distal and proximal Changbaishan ash show that this eruption generally occurred between 1,012 and 1,004 cal yr BP. Geochemical comparison between Changbaishan ash and the Quaternary widespread ash around Japan illustrates that Changbaishan ash is a continuous composition from rhyolitic to trachytic and its ratio of FeOT to CaO is usually greater than 4, which can be used as a distinguishing identifier among worldwide contemporary eruptions.

  • RESEARCH ARTICLE
    Yong ZENG,Yanpeng CAI,Peng JIA,Jiansu MAO

    Flooding is the most frequent disaster in China. It affects people’s lives and properties, causing considerable economic loss. Flood forecast and operation of reservoirs are important in flood emergency management. Although great progress has been achieved in flood forecast and reservoir operation through using computer, network technology, and geographic information system technology in China, the prediction accuracy of models are not satisfactory due to the unavailability of real-time monitoring data. Also, real-time flood control scenario analysis is not effective in many regions and can seldom provide online decision support function. In this research, a decision support system for real-time flood forecasting in Yujiang River Basin, South China (DSS-YRB) is introduced in this paper. This system is based on hydrological and hydraulic mathematical models. The conceptual framework and detailed components of the proposed DSS-YRB is illustrated, which employs real-time rainfall data conversion, model-driven hydrologic forecasting, model calibration, data assimilation methods, and reservoir operational scenario analysis. Multi-tiered architecture offers great flexibility, portability, reusability, and reliability. The applied case study results show the development and application of a decision support system for real-time flood forecasting and operation is beneficial for flood control.

  • RESEARCH ARTICLE
    Fangbing MA,Chunhui LI,Xuan WANG,Zhifeng YANG,Chengchun SUN,Peiyu LIANG

    The Danjiangkou Reservoir is the water source for the middle route of the South-to-North Water Diversion Project in China. Thus, its water quality status is of great concern. Five water quality indicators (dissolved oxygen, permanganate index, ammonia nitrogen, total nitrogen, and total phosphorus), were measured at three monitoring sites (the Danjiangkou Reservoir dam, the Hejiawan and the Jiangbei bridge), to investigate changing trends, and spatiotemporal characteristics of water quality in the Danjiangkou Reservoir area from January 2006 to May 2012. We then applied a Bayesian statistical method to evaluate the water quality comprehensively. The normal distribution sampling method was used to calculate likelihood, and the entropy weight method was used to determine indicator weights for variables of interest in to the study. The results indicated that concentrations of all five indicators increased during the last six years. In addition, the water quality in the reservoir was worse during the wet season (from May to October), than during the dry season (from November to April of the next year). Overall, the probability of the water’s belonging to quality category of type Ⅱ, according to environmental quality standards for surface water in China, was 27.7%–33.7%, larger than that of its belonging to the other four water quality types. The increasing concentrations of nutrients could result in eutrophication of the Danjiangkou Reservoir. This method reduced the subjectivity that is commonly associated with determining indicator weights and artificial classifications, achieving more reliable results. These results indicate that it is important for the interbasin water diversion project to implement integrated water quality management in the Danjiangkou Reservoir area.

  • RESEARCH ARTICLE
    Juan LI,Xiaolei ZOU

    The impact of Microwave Temperature Sounder (MWTS) radiances on the prediction of the Chinese Numerical Weather prediction (NWP) system-GRAPES (Global and Regional Assimilation and PrEdiction System) with comparison of two Quality Control (QC) schemes was researched. The main differences between the two schemes are cloud detection, O–B (brightness temperature difference between observation and model simulation) check and thinning. To evaluate the impact of the two QC schemes on GRAPES, a typhoon case study and cycle experiments were conducted. In the typhoon case study, two experiments were conducted using both the new and old QC schemes. The results show that outliers are removed in the new QC while they exist in the old QC. The analysis and the model forecast are subsequently generated after assimilating data from the two QC schemes. The model-predicted steering flows more southward with the new QC scheme, and as a result, the forecast track in the experiments is more southward, i.e., closer to the best track than the old scheme. In addition to the case study, four impact cycle experiments were conducted for 25-day periods. The results show that the new QC scheme removed nearly all the biases whereas the old scheme could not. Furthermore, the mean and standard deviation of analysis increments with the new scheme is much smaller than those of O–B. In contrast, the old scheme values are either slightly smaller or the same. Verifications indicate that forecast skill is improved after applying the new scheme. The largest improvements are found in the Southern Hemisphere. According to the results above, MWTS with the new QC scheme can improve the GRAPES forecast.

  • RESEARCH ARTICLE
    Yan YE,Xiaomeng SONG,Jianyun ZHANG,Fanzhe KONG,Guangwen MA

    Practical experience has demonstrated that single objective functions, no matter how carefully chosen, prove to be inadequate in providing proper measurements for all of the characteristics of the observed data. One strategy to circumvent this problem is to define multiple fitting criteria that measure different aspects of system behavior, and to use multi-criteria optimization to identify non-dominated optimal solutions. Unfortunately, these analyses require running original simulation models thousands of times. As such, they demand prohibitively large computational budgets. As a result, surrogate models have been used in combination with a variety of multi-objective optimization algorithms to approximate the true Pareto-front within limited evaluations for the original model. In this study, multi-objective optimization based on surrogate modeling (multivariate adaptive regression splines, MARS) for a conceptual rainfall-runoff model (Xin’anjiang model, XAJ) was proposed. Taking the Yanduhe basin of Three Gorges in the upper stream of the Yangtze River in China as a case study, three evaluation criteria were selected to quantify the goodness-of-fit of observations against calculated values from the simulation model. The three criteria chosen were the Nash-Sutcliffe efficiency coefficient, the relative error of peak flow, and runoff volume (REPF and RERV). The efficacy of this method is demonstrated on the calibration of the XAJ model. Compared to the single objective optimization results, it was indicated that the multi-objective optimization method can infer the most probable parameter set. The results also demonstrate that the use of surrogate-modeling enables optimization that is much more efficient; and the total computational cost is reduced by about 92.5%, compared to optimization without using surrogate modeling. The results obtained with the proposed method support the feasibility of applying parameter optimization to computationally intensive simulation models, via reducing the number of simulation runs required in the numerical model considerably.

  • RESEARCH ARTICLE
    Duan CHEN,Qiuwen CHEN,Ruonan LI,Koen BLANCKAERT,Desuo CAI

    Ecologically-friendly reservoir operation procedures aim to conserve key ecosystem properties in the rivers, while minimizing the sacrifice of socioeconomic interests. This study focused on the Jinping cascaded reservoirs as a case study. An optimization model was developed to explore a balance between the ecological flow requirement (EFR) of a target fish species (Schizothorax chongi) in the dewatered natural channel section, and annual power production. The EFR for the channel was determined by the Tennant method and a fish habitat model, respectively.βThe optimization model was solved by using an adaptive real-coded genetic algorithm. Several operation scenarios corresponding to the ecological flow series were evaluated using the optimization model. Through comparisons, an optimal operational scheme, which combines relatively low power production loss with a preferred ecological flow regime in the dewatered channel, is proposed for the cascaded reservoirs. Under the recommended scheme, the discharge into the Dahewan river reach in the dry season ranges from 36 to 50 m3/s. This will enable at least 50% of the target fish habitats in the channel to be conserved, at a cost of only 2.5% annual power production loss. The study demonstrates that the use of EFRs is an efficient approach to the optimization of reservoir operation in an ecologically friendly way. Similar modeling, for other important fish species and ecosystem functions, supplemented by field validation of results, is needed in order to secure the long-term conservation of the affected river ecosystem.

  • RESEARCH ARTICLE
    Weiying ZHANG, Inchio LOU, Wai Kin UNG, Yijun KONG, Kai Meng MOK

    Freshwater algal blooms have become a growing concern world-wide. They are caused by a high level of cyanobacteria, predominantly Microcystis spp. and Cylindrospermopsis raciborskii, which can produce microcystin and cylindrospermopsin, respectively. Long-time exposure to these cyanotoxins may affect public health, thus reliable detection, quantification, and enumeration of these harmful algae species has become a priority in water quality management. Traditional manual enumeration of algal bloom cells primarily involves microscopic identification which limited by inaccuracy and time-consumption. With the development of molecular techniques and an increasing number of microbial sequences available in the Genbank database, the use of molecular methods can be used for more rapid, reliable, and accurate detection and quantification. In this study, multiplex polymerase chain reaction (PCR) and real-time quantitative PCR (qPCR) techniques were developed and applied for monitoring cyanobacteria Microcystis spp. and C. raciborskii in the Macau Storage Reservoir (MSR). The results showed that the techniques were successful for identifying and quantifying the species in pure cultures and mixed cultures, and proved to be a potential application for water sampling in MSR. When the target species were above 1 million cells/L, similar cell numbers estimated by microscopic enumeration and qPCR were obtained. Further quantification in water samples indicated that the ratio of the estimated number of cell by microscopy and qPCR was 0.4–12.9 for cyanobacteria and 0.2–3.9 for C. raciborskii. However, Microcystis spp. was not observed by manual enumeration, while it was detected at low levels by qPCR, suggesting that qPCR is more sensitive and accurate. Thus the molecular approaches provide an additional reliable monitoring option to traditional microscopic enumeration for the ecosystems monitoring program.

  • RESEARCH ARTICLE
    Yanying BAI, Thomas A. SCOTT, Qingwen MIN

    Soil temperature plays an important role in physical, biological, and microbiological processes occurring in the soil, but it is rarely reported as an indicator of climate change. A long-term soil temperature database, collected in the Mojave Desert region from 1982–2000, was used to examine the relationship between regional climate change and soil temperature. During this 19-year study period, there was a warming trend in the Mojave Desert region. The soil temperature in this region, measured at 50-cm deep, increased at an average rate of 0.79°C per decade. The temporal changes of soil temperature and those of air temperature were highly correlated. Elevation was the dominating factor that affected the spatiotemporal variations of soil and air temperature.

  • RESEARCH ARTICLE
    Zhongsheng CHEN,Yaning CHEN

    The aim of this study was to analyze the effects of climate fluctuations on runoff in the headwater region of the Kaidu River in northwestern China. For this purpose, precipitation and potential evaporation (PET) data from 5 meteorological stations and the runoff depth data from the Dashankou hydrological station in the headwater region of the Kaidu River from 1960 to 2009 were collected, then the trends and abrupt changes of precipitation, PET and runoff depth were analyzed by means of Mann-Kendall test (M-K test) and Mann-Kendall-Sneyers test (M-K-S test), respectively. The runoff model driven by precipitation and PET was developed in this work and the sensitivity of runoff to climate fluctuation was simulated under different scenarios. Results showed that the annual precipitation and runoff depth both exhibited an increasing trend over the periods 1960–2009; however, this is not the case for the annual PET. The abrupt changes for annual precipitation, PET and runoff depth all occurred in the early 1990s. The established driving model could well reflect the complicated nonlinear relationship among runoff depth, precipitation and PET. The sensitivity analysis indicated that the precipitation had a positive effect on the runoff depth, opposite to what were observed between PET and runoff, and the runoff depth was more sensitive to precipitation than to PET in the headwater region of the Kaidu River.